The goal of the present proposal is to determine the mechanism of glomerular injury (focal glomerulosclerosis) in patients with opioid abuse. Since expansion of mesangium is considered a precursor of glomerulosclerosis, the objective of the present application is to examine whether opioid use is associated with mesangial expansion, and if it is, is it caused by an increased delivery of macromolecules into the mesangium or by an increased synthesis of mesangial matrix or both. To determine the role of mesangial cells (MC) in this lesion we intend to a) study the presence of opioid receptors on mesangial cells; b) determine the effect of opioids on uptake of IgG complexes and associated release of lipid mediators of inflammation and reactive oxygen species by MC and macrophages; c) evaluate opioid induced cytoskeletal changes in mesangial cells and matrix. A number of methods will be used. These include quantification of IgG complex uptake by mesangial cells using reflectance microscopy and radiolabeling; determination of lipid mediators of inflammation (PGE2,PAF) and reactive oxygen species (superoxide and hydroxyl radicals); morphometric analysis of the size of mesangium (in vivo); mesangial localization of cytoskeletal changes by fluorescence technique using video enhancement and the confocal microscope to determine structural changes at high resolution. The hypothesis for opioid action will be tested based on preliminary findings that MC have receptors for opioids and opioids cause attenuation of growth of MC and may thus cause accumulation of phlogogenic macromolecules in the glomerular mesangium. This may lead to an initial mesangial expansion and subsequent sclerosis. These findings will increase the understanding of glomerular lesions in patients with drug abuse, where little work has been done. It will increase our understanding of the response of the mesangial cells, and important contribution of renal function.